The proposed research will examine the role of environmental and constitutional factors in the regulation of sleep behavior and sleep-influenced physiological variables in the aged cat. Longitudinal changes in EEG state-pattern characteristics and breathing parameters will be assessed as will the effects on sleep of exercise, environmental temperature, and partial and total sleep deprivation. The overall aims of this work are: i) to broaden an understanding of sleep mechanisms and sleep-related pathology in senescence and ii) to identify safe and effective means of improving sleep efficiency in the elderly. Young adult (2-4 years) and old (greater than 11 years) cats will be surgically prepared with indwelling electrodes for chronic recording of EEG, EOG, and EMG, and lateral geniculate activity. Respiratory variables will be measured using both inductive plethysmography and pneumotachography. Data will be evaluated by visual inspection and computer analyses.